1. Field of the Invention
The present invention relates to a pivotal structure for an impeller shaft of a miniature heat dissipating fan
2. Description of the Related Art
Taiwan Utility Model Publication No. 355037, issued on Mar. 21, 1999 and entitled "IMPROVED BEARING LUBRICATION FOR A BRUSHLESS D.C. FAN", discloses an oil-pregnant bearing with a bore for receiving an axle, wherein a reservoir is defined in a middle portion of the bearing bore for receiving lubrication oil, and the pivotal seat of the fan housing includes a number of grooves for containing lubrication oil of the lubrication oil supply system.
It is, nevertheless, found that the bearing and the axle have a considerable contact surface area for rotation and thus have a larger frictional surface. Thus, noise tends to occur after a long-time use. In addition, the manufacture of the above-mentioned structure is troublesome and the cost therefor is high.